Process of color photography



Patented May 18, 1943 UNITED STATES PATENT OFFICE I i'I KOtIESS oifszii i no'roonarri Virgil B. Sease, New Brunswick, and John R- Weber, South River, N. 1., assignors, by mesne E I. du Pont de Nemours &

assignments, to

Company, Wilmington;

Delaware Del., a corporation of No Drawing. Application July 28,1939,

Serial No. 287,154

I 11 Claims. ((31.9%2)

- This invention relates to color'photcgraphy and more particularly to methods of producing colored images in multilayer photographic elements. More particularly it relates to novel multilayer photographic elements containin colorformers and to a novel process for producing colored images in a multilayer film.

A further object is to produce a multilayer filmwhich may be processed in a simple manner to form a color photograph. A still further object is to provide a color'printing stock which faithful- -ly and accurately records a.color ed scene. A still further object is to'provide a process for developing and processing multilayer film to produce a color photograph which involves a few simple steps. A still further object is to provide a process for developing and processing an exposed multilayer film to a multilayer, color photograph which can bepracticedby the average photographer. Still other objects will appear hereinafter.

, Many methods paring colored photographs, but event the most improved of these, particularly those dealing with superposed multi-layer film requires such adegree of skill and control that the average photographer cannot process his own exposures. Furthermore, the large number of steps involved in processing film by prior art methods renders the cost prohibitive to many photographers. The previous methods of color cinematography involving superposed multilayer film fall into two general classes: -(1) those in which the respective ohotosensitized layers are uniformly colored and the color is discharged differentially with respect o the silver images formed by development. (2)

those in which colors are formed step-wise and I difl'erentially. in respect to ,the silver images formed-by development. Each of these processes is quite involved and requiresa great deal of hanlling of the film. The first-mentioned process known commonly as a bleach-out process, deends upon the bleaching-out or removing of dye in direct proportion to the density of the silver in the image. In actual practice it has been diilicult to bleach out the dyes entirely in those areas which should be clearof dye. Vari ations and impurities in the dyes themselves.

variations in dyes of thesame nameor indexnumber but made by different manufacturers,

variations in the purity of the chemicals of the bleach-bath and local variations in the rates of have been suggested for prevolume production of colored photographs by this penetration of these baths through the multielayers, have made this process incapable of producing colored photographs on a'volume basis.

The second process is even more delicate in its processing requirements since it depends on the controlled diffusion of developers, bleach-baths and stop-baths through thin layers of gelatin. Variations in coating weight, hardness of gelatin. swelling characteristics of the gelatin, temperature of baths, etc., make extremely diflicult the method.

The above disadvantages are overcome and the objects hereof are obtained by the hereinafter described invention by the use ,of a novel arrangement of superposed multilayer photographic emulsions and a novel and simplifiedmethod of processing. i I The novel film is composed of a transparent base having at least two differentially sensitized emulsion layers containing color-formers superimposed thereon, one of the emulsion layers being imposed directly upon the base and being further characterized in that a layer of prefogged silver salts is interposed between said emulsion layers.

In the case of three-color photography, two emulsion layers may be placed upon one side of the base and one emulsion layer placed upon the reverse side of the base. In this embodiment of the invention only one pre-fogged silver salt layer is necessary, but two may be employed, one being coated directly on the base. In other embodiments wherein three superimposed layers arev on the same side of the base two pre-fogged silver salt layers are employed being placed between the emulsion layers. Color formers as above stated are incorporated in the respective emulsions.

Film suitable for two color photography may consist of a. film base having two superposed emul- 1 Sim layers on one side of the base and a prefogged silver salt layer between'the sensitized emulsion layers or the emulsion layers may be placed on each side of the base, a pre-iogged layer I being between one of them. 1

The novel film constructions hereof, when used for recording an original scene, can be classified as a negative filmand is'composed of a series of photo-sensitive silver salt emulsion layers which are individually sensitized to record blue, green.

I developer in a reversal process may be used for amidol developers. The development at this A yellow filter layer is also embodied in the film so that the red layer will not be exposed to the blue-green end of the spectrum,- e. g. green, blue, violet and ultra-violet.

In one important embodiment of the invention '5 the layers are so arranged'that light from the scene is first incident on a blue sensitive layer which contains a yellow color-former. A yellow filter dye, e. g. Luxol Fast Yellow T, may be incorporated in the blue sensitive layer or in a sublayer of gelatine. The light then passes through a pre-fogged emulsion layer, then a green sensitive emulsion layer containing a magenta colorformer, then a pre-fogged emulsion layer containing a soluble red dye (e. g. 'carmosine M), a red sensitive emulsion layer containing a bluegreen color former and finally through the base.

The amount of silver-salt in these pre-fogged layers, and the fogging exposure given these emulsion layers is preferably such that upon the .first development of the layers a. light-barrier layer will be formed in these pre-fogged emulsions so that substantially less than 1% of light will be transmitted by either of'them. The present inventionthereby provides for an effective control of the printing light penetration by means of the black barrier layers formed from the pre-fogged emulsion layers by the first development step.

In using the film just described, it is exposed normally in a camera, after which it is given a 30 development treatment in a bath containing a non-color-forming developing agent. Any suitable developer which is of the type used as a first this purpose, preferably an energetic-working developer to give full detail and harmonious color rendering. It is alsodesirable that the developer selected produce a minimum of relief effect in the l gelatin. To this end, caustic alkalies should be avoided. Sodium carbonate is preferable as an 40 alkali and is used in smaller amounts than generally used in reversal first developers. Metol in combination with hydroquinone, for instance, is suitable as the developing agent, as are also acid stage should be carried out completely, that is none of the latent images should be left undeveloped.

After development and washing the film consists of three color separation negative image layers bearing both silver and unexposed undeveloped silver-salt images and two layers of metallic silver in which there may be small amounts of non-color sensitized silver salts. The film is now preferably exposed through the base with a red or white printing light which exposes only the silver-salt image remaining in the red sensitive layer. The printing light does not ,alfect'the other two layers because of their lack of sensitivity to thered light, but primarily because the 69 black metallic silver barrier-layer prevents substantially all of the printing light from passing through to other laye The film is now developed in a solution com taining a color-developing agent, preferably an aromatic diamino developing agent, which will couple with the blue-green-to form a dye image in situ with the silver.. A suitable developer for this purpose is as follows: V

Developer A Potassium carbonate grams 30 Sodium sulfite, anhydrous ..do.- 5 Diethylalnino aniline hydrochloride ..do:.e.; 3 73 1| 1 water dye images from the exposed silver halides of only the red-sensitive layer. The film is then thoroughly washed.

The top or blue sensitive layer is now exposed to a blue or preferably white printing light. The printing light does not have any substantial effect upon the middle or blue-green sensitive layer because of the metallic silver barrier layer between the top and middle layers. The entire film is then treatedin a developing solution which contains a developing agent which will couple with the yellow color-former. A suitable developer solution is Developer A. After development the top layer will contain both metallic silver and yellow dye images in situ therewith.

There now remains the green-sensitive middle layer on both sides of which are black, metallicsilver barrier layers. This central layer is preferably chemically exposed by bathing the film in a solution of a mild inorganic reducing agent, e. g. 0.5% aqueous solution of alkaline sodium arsenite or a 5% aqueous solution of hydrogen peroxide. This chemical exposure will make sensitive the silver salts remaining in the middle layer.

As another means of chemical exposure the film may be treated with an aqueous solution of an organic sulfur-bearing compound such as a 5% aqueous solution of guanidine thiocyanate or guanyl thiourea, thiourea, allyl thiourea, imino amino sulfinic acid of a pH of at least about 7.1.

It is not necessary, however, to resort to chemical exposure of the middle layer to render it exposed or so that the silver salts are sensitized. Thus, the middle layer may be exposed by means of x-ray exposure of the entire'fllm, or by means of mechanical vibrations of a class known as ultrasonic" vibrations. In the latter case the entire film, during the latter part of the washing operation following the yellow development, may

be subjected to ultrasonic vibrations, or the film,

after washing may be immersed in water or some non-film solvent and then subjected to ultrasonic vibrations. The central layer can also be exposed by means of heat rays, in which case the entire film should be immersed in 5% formaldehyde solution before exposing to the heat rays.

After the middle layer has been exposed, the entire film is treated or developed in a solution containing a developing agent which will couple with the magenta or minus-green color former to form a magenta dye upon development. A suitable developer is Developer A above described.

After this final development, the silver is removed from all the layers by means of a photov graphic reducing bath. Any of the conventional reducing. baths may be used at this stage or the process. Suitable baths include Farmers Reducer and permanganate, sulfuric acid. The former'may be used either as a combined bath or separately; by immersing the film in a 5% solution of ,potassium ferricyanide and then in a 20-40% sodium thiosulfate solution. The sulfamic acid bleach bath of McQueen and Goebel application, Serial No. 233,117. filed- October 3, 1938 now U. S. Patent 2,195,419, may also be used.

In a modification of the invention which is of considerable importance a green blind red-sensitive layer occupies the central position of the multilayer film. This green-blind red sensitive layer is sensitized by means of pinacyanol or one of the naphthoseleno carbocyanlnes such as symsteam could escape.

. was replaced as it boiled ofl. Finally the crucible 333' diethyl-naphthoselenocarbocyanine iodide described in co-pending application No. 78,734,

filed May 8, 1936, or the green blind sensitizing dyes described in U. s. Patents 2,148,979, 2,148,-

980, and Piggott and Rodd U. 8. Patent 2,011,898. The sym-3:3' diethyl-naphthoselenocarbocyanineiodide was prepared byre acting one part one part of ethyl-ortho-formate in the presence of 6 partsof dry pyridine by heating the admixture under reflux for 20 minutes. The 2-methyl-alpha-naphthoseleno ethiodlde was prepared by reacting 2-methyl-alpha-naphthoselenazole with three mols of ethyl iodide under reflux for 24 hours, evaporation of the excess ethyliodide and crystallization of the product from alcohol. The base was made in the following manner:

, thalene nucleuafor instance,may contain methyl,

or of 2-methyl-alpha-naphthoseleno ethiodide with I ethyl, or propyl methoxy or ethoxy radicals'in one or more of the 3-, 4-, 5-, 6-, 7-, or 8-positions. The quaternary salts may be condensed to form cyanine dyes in like manner. The multilayer film used in this modification consists of a support coated on one side with a green sensitive emulsion containing a magenta color former,.

then a. pre-fogged layer on which is coated a green-blind red-sensitive emulsion containing a blue-green color former on which is coated a blue-sensitive emulsion containing a yellow colorformer. The last mentioned layer may contain yellow filtering agent, e. g. titanium ferrocyanide, or the yellow filter may be incorporated in a separate gelatin sub-layer.

In using the just described film, it is exposed I normally in a camera with the emulsion facing A solution of 51 parts of the hydrochloride of 1-bromo-2-aminonaphthalene in about 70 parts of alcohol was treated with 28 parts of potassium selenocyanate in 80 parts of water. After standing over night at room temperature, the mixture was evaporated to dryness and extracted many times with hot water. The extract was made alkaline with ammonia and the aminonaphthoselenazole' precipitated. It was recrystallized from alcohol. Yield 36 parts; M. P. 252 C. This compound has the formula: v

A mixture of 28 parts 0! the aminonaphthoselenazole, 28 parts of sodium hydroxide and 50 parts of water was heated together in an nickel crucible for three hours on an electric hot plate.

The cover of the crucible was adjusted so that Water lost by evaporation was evaporated to dryness and heated until the fumes due to decomposition began to appear. The residue was taken up with water and filtered. The filtrate was cooled, and dilute hydrogen peroxide added dropby-drop until no more precipitation formed. The precipitated diseienide, a

yellow amorphous powder, was, separated by filtration, washed and dried. A yield of 13 parts was obtained. This compoundhas the formula:

se-s' NE. NH

" This was heated to bcii ns n 108 parts of acetic anyhdride under. a recur condenser and 4 parts of zinc gtaduailysdded. Heating was pling under the development conditions with the T central layer;

the lens. It is then processed to colored positives by the following steps:

11. Develop in a non-color forming developer.

e. g. of the .type hereinbefore described;

2. After washing, the film is flashed through the base with white or green. light which exposes the green sensitive layer but not the red or blue layers due to the barrier layer of .metallic silver formed by the first development;

3. The film is then developed in a solution containing a developing agent capable of consensitive layer;'

'7. The film is now developed after the manner of step 3 to form a yellow dyed image and metallic silver;

- 8. After washing the silver deposits in the emulsion and barrier layers are removed by means of a'reducing agent such as Farmer's Reducer or .by treatment with cupric bromide,

followed by a clearing bath of hypo and a final Wash.

A film similar to that just described but which has the greensensitive layer on one side ofthe base and the green-blind, red sensitive, and blue sensitiv layers mounted upon the oppositeside is made. In this modification a pre-fogged layer 8 is placed between the green-sensitive layer and continued for thirty minutes. The hot solution 5 was filtered from some unreacted zinc, and poured into water. The solution was later extraded with ether, and after drying the other solution and removing the etherby evaporation, needle crystals of the Z-methyl-alpha-naphthoselenazole were obtained. It m'eltedat 81-82 C.

Yield 7 parts. r

In "a manner similar to that 'just described, other 2-methyl-naphthoselenazoles and their quaternarysalts may be prepared. The naphthe base, but no pre-fogged layers are placed upon the other side between'the green blind and blue sensitive emulsion layer. This type of\ film contains the same type of color-formers and may 'be processed in the same manner as immediately preceding y I Another 'film construction which can be proceased by the processes hereof comprises a film .base having a pre-fogged layer, preferably containing a, red dye, on one side of a transparent film base over which'is coateda red sensitive layer containing a blue-green color-former, on

the other side of the base is first a green sensitive layer containing a magenta color former,

next a pre-fogged silver halide layer, and finally, a blue sensitive layer containing a yellow color former. This-film may be processed in the first example.

The invention, however, is not limited to three color photography, but on the contrary, can be Y used with two color photography, wherein a prefogged layer is placed between two differentially sensitized emulsion layers containing color formers, either directly or indirectly by reason of one layer being disposed upon the opposite side of a film base.

A film similar to that used in the preceding modifications is employed for the multi-color positive prints. In this modification, three color-separation negatives are required. These may be made in a camera or from a colored transparency or from a colored reflection print or by reflection copying. Positive prints in black and white may be made from these negatives or the negatives themselves may be reversed into positive records. Three positive separation records are printed onto the'multilayer film previously described. The sequence of printing operations is not important but the following serves as being illustrative of a preferred procedure:

(a) The blue record positive is printed by white or blue light onto the top layer;

veloper of a reversal process and the film is processed to color by following through the steps two to eight inclusive as described in the preceding modification. Thereare a great many color-formers which can be used in the processes described herein and it is to be distinctly understood that the invention is not limited to any particular class or classes. They are'preferably non-migratory.

As examples of suitable non-migratory yellow color-formers which may b used in the bluet sensitive layer, mention is made of the diacylacetamino-aryl-bis-thiazoles of U. S. Patent 2,140,- 540, of which difuroylacetamino-1,2,4,5-benzobis-thiaz ole and di-acetoacetamino-1,2,4,5-benzobisthiazole are especially useful as are 2-hydroxy 3 naphthoylaminobenzoyl acetanilide, sodium stearoylamino-benzoylacetanilide-p-carbolylate, p-caproylamino, benzoylamino salicylic acid, furoylacet-p-amino phenyl-amyl ether (described in Jennings and Middleton application,

Serial No. 215,702, filed June 24, 1938, now U. S.

Patent 2,184,303), and di-picolinoyl-acet benzi- 'dine. Suitable non-migratory magenta. color-formers which are especially useful are 1-(3'-sulfophenyl) -3-(4" -.stearoyl-amino phenyl) -5-p'yrazolone sodium salt, 1-(4-oxy-3'-carboxyphen- -yl) -3-(4"-dodecoylamino pheny1) 5 pyrazolone, 4,4'-di (carboyl 1-p aminophengl-B- methyl-5-pyrozolone) razolonyl-1")-'diphenyl (described in Jennings 2,319,369 the nlngs, Serial No. 256,201, filed February 13, 1939, now U. S. Patent 2,294,909).

Suitable non-migratory blue-green color formers of especial utility include 4,4-di-(1-hydroxyoyl 4 N (1' oxy 2' naphthoyl) phenyl enediamine sodium sulfonate, resorcinol mono-ndodecyl ether (described in Salzberg and White, Serial No. 164,984, filed September 21, 1937, now U. S. Patent 2,166,181), product of p-hydrorwbenzoic acid and formaldehyde (described in Mc- Queen, Serial No. 261,794, filed March 14, 1939),

plurality of amino groups or substituted aminogroups and/or hydroxy groups. They must, however, contain at least one unsubstituted amino group (-N'Hz).

The preferred developing agents in the process of dye coupling development are derivatives of p-phenylenediamine and particularly the asymmetric dialkyl p-phenylenediamines, e. g. paminodimethylaniline, p-aminodiethylaniline, paminodibutylaniline, etc. Other developing agents which may be used include p-phenylenediamine itself, p-methylaminoaniline, p-ethylaminoaniline, p-aminophenol, 1 N,N-diethyl-ophenylene-diamine, chloro-p-phenylenediamine, 1,2,5 toluylenediamine, 2 amino 5 diethylamino toluene, N p aminophenylpiperidine, N methyl N hydroxyethyl p phenylenedi amine, N butyl N hydroxyethyl p phenylenediamine, p 'y dihydroxy propyl p phenylenediamine, 2 amino 5 (N B hydroxy ethyl N butyl) aminotoluene and its dihydrochloride, etc. These aromatic aminodeveloping agents may be used in the form of their salts, which may be either inorganic or organic. than the free bases. As examples of suitable salts mention is made of the hydrochloride, sulfates, acetates, etc.

The novel film constructions of the present invention containing color-formers in the emulsion velopment, and since the amount of development is functional with the amount of silver halides exposed, the 'barrier layers of metallic silver allow the outer emulsions to be controlledand Middleton, Serial No. 215,703, filed June 24,

1938, now U. S. Patent 2,200,924), 4,4'-methylene-bis- (m-stearoylaminophenyl) -methyl pyra- 201, filed February 13, 1939, now U. S. Patent 2,294,909), and 4,4'-o sulfo-benzylidene-biszolone (described in Jennings, Serial No. 256,-

(phenyl methyl pyrazolone) (described in Jenexposed by the second exposure of the reversal process in accordance with the dye-forming characteristics of the individual layer.

Inorder to determine the amount of second exposure, a test strip of film, given a very slight over-all exposure to white light, is processed through by any of the above-described methods. The processed film should, if the dye-coupling The salts are in general more stable Inasmuch as, for a given color from that balance is correct, produce an overall neutral gray density. If the dye-coupling rate is offbalance in one of the layers, the film will show a decided color and will not be neutral gray. Thus, if the yellow color-forming layer is too slow'in its dye-forming, theresulting film will be bluish; if the blue-green layer is slow, the film will be reddish; if the middle one is slow it will be greenish. If the chemical exposure has been too light, the final film will be greenish. Thus, by means of thisv slightly-flashed teststrip on the raw stock (which may be an unexposed end of the roll or a piece of the cut film), the dye-forming characteristics of the emulsion are predetermined and the amount of second exposure, both chemical and light, are determined in accordance with the dye-forming characteristics of the individual emulsion layers.

(2) The different color-formers have different effects on the emulsions. Some color-formers sensitize and fog the emulsion layers, thus producing more dye density than ordinarily. Others may decrease emulsion speed thus yielding less dye density than should be expected. Bycontrolling the amount of second exposure, thesevariations in emulsion characteristics, (and thus variations in dye-densities), can be compensated for by first determining the dye-forming characteristics of the film as described above.

(3) Lack of uniformity from batch-to-batch of color-former likewise causes variations in the characteristics of the final dye images. These variations are compensated for in a similar manner as described above. Thus, the present invention includes the method of processing such fogged barrier layer films by varying the second exposure in accordance with the dye-generating characteristics of the individual emulsion layers.

As many apparently different embodiments of this invention may be made without departing from the spirit and scope thereof, it is to be unof each of said layers being imposed directly upon the base and a layer of pre-fogged silver salts interposed between each of said emulsion layers.

4. A photographic element comprising a transparent base having three emulsion layers sensitized red, green and blue, respectively, superposed thereon, the red layer being imposed directly on the base, a non-migratory color-former in each of said emulsion layers capable of yielding a oye complementary in color to the sensitivity of the respective layers upon color coupling development, a pre-fogged silver salt layer interposed bederstood that we do not limit ourselves to the specific embodiments herein except as defined by the appended claims.

We claim: I

l. A photographic element comprising a transparent base having at least twodifferentially sensitized emulsion layers each containing a nonmigratory color former capable of forming a dye by color coupling development superimposed thereon the color. formers of the respective layers being capable of forming a dye different in color one of said from that formed in the other layers, layers being imposed directly upon the base and a layer of pre-fogged silver salts interposed between said emulsion layers.

2. A photographic element comprising a transparent base having at sensitized emulsion layers containing non-migratory color-formers superimposed thereon, one of said layers being imposed directly upon the base and a layer of pre-foggedsilver salts interposed between said emulsion layers, the color-formers in the respective layers forming dyes upon, development which are complementary in color to the color sensitivity of the respective emulsion layers. I

3. A photographic element comprising a transparent base having at least three differentially sensitized emulsion layers superimposed thereon, each containing a non-migratory color former capable of forming a dye by color coupling development, the color formers of the respective layers being capable of forming adye different in formed in the other layers, one

least two differentially tive emulsion layer containing tween each of the emulsion layers.

5. A film element comprising a transparent base, a red-sensitiveemulsion layer containing a l non-migratory blue-green color-former imposedv directly on said base, a pre-fogged silver salt layer imposed on said red layer, a green-sensitive layer containing a non-migratory magenta color-.

' former imposed on said pre-fogged layer, a prefogged silver salt layer, and finally a blue sensitive layer containing a non-migratory yellow color former.

6. A film element of the type set forth in claim -5, wherein a yellow filter layer is positioned in front of the red sensitive layer.

7. A film element comprising a transparent base, a green-sensitive emulsion layer containing a non-migratory magenta color-former imposed directly on the .base, a pre-fogged silver salt layer imposed on said green sensitive layer, a greenblind panchromatic layer containing a nonmigratory blue-green color former, a blue-sensia non-migratory yellow color former imposed on said panchromatic layer. l

8. A photographic element as set forth in claim '7, wherein a yellow filter layer is positioned in front of said panchromatic layer.

9. The process for forming a multicolor picture on the photographic element of claim 1, which comprises exposing said element to form color separation records of an object, developing therein partial images of said object in a noncolor forming developer, re-exposing the remaining sensitive salts in the outer sensitive layer,

developing the said sensitive layer in with an aromatic amino developing agent having an unveloping agent having an unsubstituted amino group and removing all silver formed by the forerespective emulsion going steps.

10. A process for forming a multicolor picture in the photographic element of claim 3, which comprises exposing said element to form color separation records of an object, developing therein the partial images of said object, re-exposing the remaining sensitive salts, in the two outer layers by respectively exposing them to light having the same wave length as that to which the layers are sensitive and developing said layers with an aromatic amino developing agent having an unsubstituted amino group, chemically exposing the middle layer, de-

, veloping said layer with an aromatic amino de- "veloping agent having an unsubstituted amino group and removing all silver formed by the foregoing steps.

- 11. A process for forming multi-color pictures which comprises developing an exposed test strip of a film element of the type set forth in claim 3, developing the strip in a non-color forming developer, re-exposing the remaining salts in one 6 of the outer sensitive layers and developing said layer with an aromatic amino developingagent having an unsubstituted amino group, re-exposing the salts remaining in the other outer sensitive layer and developing said layer with an arcmatic amino developing agent having an unsubstituted amino group, chemically exposing the middle layer and developing the same with an aromatic amino developing agent having an unsubstituted amino group; removing all silver formed by the foregoing steps; and regulating the processing of the film element in accordance with the dye-forming characteristics of the individual emulsion layers.

VIRGIL B. SEASE.

JOHN R. WEBER. 

